Synthesis and characterization of oxides for symmetrical and intermediate temperature SOFC

A SERQUIS; F. NAPOLITANO; A. SOLDATI; A. FERNANDEZ ZUVICH; L. BAQUÉ; J. GECK; D. G. LAMAS; H. TROIANI; C. GONZALEZ OLIVER; A. CANEIRO

Campos do Jordaõ

Congreso; XII Encontro da SBPMat; 2013

SBPMat

In this talk I will present some of the last results obtained in the research on ceramic materials for solid oxide fuel cells (SOFC) performed in our group. The focus is the correlation between the microstructural aspects (determined by the processing parameters) and their physical properties that determine the materials efficiency. The structural stability and chemical compatibility between the electrode and electrolyte materials studied are evaluated through the combination of several characterization techniques, such as electron microscopies (SEM, TEM), X-ray diffraction (XRD), chemical analysis by EDS and synchrotron radiation methods (XANES  y EXAFS). Due to the diversity of analyzed materials, in this talk I will focus in two systems: The first one involves electrolyte and electrodes materials for intermediate temperature SOFC (IT-SOFC). One example is the study of interfaces between gadolinium doped ceria (CGO) as electrolyte and nanostructured La1-xSrxCo1-yFeyO3-d (LSCFO) as cathode [1]. In this case the transport and electrochemical measurements, which take into account electrons and ions transference through the interfaces and electrode reaction mechanisms, will be correlated with the microstructure aiming to understand charge transfer and electrode reaction mechanisms. Another example is the morphological and structural characterization of thin Ce0.9Gd0.1O2-δ  electrolytes prepared by a tape-casting technique. The second system is the research involving the synthesis (by a low-temperature chemical route) and the structural characterization of lanthanum strontium titanates based oxides. These materials with perovskite-type crystal structure (ABO3) are promising electrodes for the recently proposed symmetrical solid oxide fuel cells (SSOFC).  In particular, I will present a combined Synchrotron XPD, XANES and EXAFS study of La0.4Sr0.6Ti1-yCoyO3±d (0 £ y £0.5) [2, 3]. For example, a rhombohedric to cubic phase transition was established for y > 0 compositions, which temperature depend on the Co content. Besides, we observed a high stability of the Ti4+ that triggers the A-site deficiency in low Co content samples and predicts that oxygen vacancies are much more easily formed at large y values, which in turn will greatly enhance the performance as electrode material.